Our Autism Center of Excellence (ACE) aims to discover the mechanisms related to early brain overgrowth in autism and to define specific behavioral and biological factors associated with infants at-risk for the disorder. These goals can only be achieved if autism is studied prospectively. Currently, the only prospective strategy in use is the baby-sibling design. Unfortunately, the baby-sib approach is weighed down by heavy research costs, long time frames to identify and follow cases, and only represents autism as it occurs in multiplex families. The Clinical Phenotype: Recruitment and Assessment Core (CPRAC) will implement a different strategy, called the 1-Year Well-Baby Check-Up Approach, to identify and study infants at risk for an ASD prospectively. As shown in the preliminary results section, this approach has the potential to identify at-risk cases quickly, and for a fraction of the cost of baby-sib research. Importantly, this unbiased approach will identify ASD cases from singleton and multiplex families alike, and as such may more realistically represent the population of autism. This method will allow infants at-risk for an ASD as well as those at-risk for a developmental disorder (DD) to participate in MRI (Project 1), fMRI (Project 2) and genetic research studies (Projects 3 and 4) beginning at 12-months in age. The CPRAC will also recruit, using the same approach, age, gender and ethnicity-matched typical controls. Thus, the CPRAC will recruit a total of 3 study groups: at-risk ASD, at-risk DD, and typical. The CPRAC will also thoroughly characterize each study infant using standardized clinical and experimental measures in the general areas of social, cognitive, language, and exploration behavior. Infants will also receive a thorough physical and neurological examination and have blood samples collected through CPRAC services. The CPRAC will follow infants longitudinally and collect selected study data every 6 months until each participant turns three years old. CPRAC investigators will implement quality control of assessments and adhere to all research subject protection guidelines including HIPAA. In summary, the CPRAC will be responsible for: 1) identification and recruitment of 12-month old infants; 2) diagnostic and psychometric evaluations of study infants every 6 months 3) coordination of each infant's participation in Projects 1-4;4) final diagnoses when each participant turns three. The CPRAC will also be responsible for informed consent and ensuring compliance with current clinical and research standards and guidelines, including HIPAA. The CPRAC will also work closely with investigators on each of the projects, as well as the other Cores.